Clamp



July 15, 1958 E. A. LINDGREN CLAMP 2 Sheets-Sheet 1 Filed Aug. 15?, 1955INVENTOR y ,1958 EQ A. LINDGREN 2,842,814

CLAMP Y Filed Aug. 15, 1955 2 Sheets-Sheet 2 Z /09 5k fif 7 F r IN 2 ENTOR.

CLAMP Erik A. Lindgren, Chicago, In.

Application August 15, 1955, Serial No. 528,40)

11 Qlaims. (Cl. 20-92) This invention relates to fastening means for thesections of a demountable enclosure and more particularly to a concealedclamp for securing adjacent section frames of a screen room used forelectromagnetic and electrostatic shielding in tightly abuttingalignment.

It is highly important that the electromagnetic and electrostatic waveshields of the screen room should have their individual screen sectionsin firm electrical contact along the corresponding marginal edges sothat the quality of wave attenuation may be uniform and sustained. Thismay be accomplished in part by the manner in which the screen sectionsare secured to the frames. but in addition the fastening means for theframes must be adequate to overcome variations in manufacturingtolerances and to afford easy assembly and disassembly so that theframes and screens will not be damaged. The fastening means currently inuse, which utilize nails and screws and the like, do not afford anyadjustment in the tightness of fit be tween adjacent frames such aswould maintain the contact between respective screen sections despiteminor variations in construction, and furthermore such means oftenoccasion damage to the frames, and the effort involved in inserting andremoving nails or screws is considerable.

Accordingly, it is an object of the present invention to provide a clamphaving separable parts which may be mounted individually on respectivesections of a screen room in a predetermined appropriate alignment withthe frame ele ents and which permit the frames to be fastened easily andsecurely in proper relationship.

Another object is to provide a clamp of the type indicated which isadjustable, so that the tightness of the lit between adjacent frameelements may be varied in order to hold the screens in uniformelectrical contact despite differences in manufacturing tolerances, andso that only one clamp will be required at each clamping point, withpreferably three clamping points vertically spaced at each verticaljoint between frame elements.

Another object of the invention is the provision of means for lockingadjacent frame members in the desired position after they have beendrawn into tightly abutting relation as described.

Another object is to provide release means for disassembly of abuttingframe members which requires a minimum of exertion and which entails nodamage to the frames themselves.

Other objects and advantages will become apparent as the descriptionproceeds in accordance with the drawings, in which:

Fig. 1 is perspective view of a screen room for electrostatic andelectromagnetic wave attenuation embodying the clamp of the presentinvention;

Fig. 2 is an exploded enlarged perspective view of the clamp accordingto the invention;

Fig. 3 is a horizontal sectional view of the clamp accordin g to theinvention including a fragmentary view of frame elements for the screenroom taken along the lines 33 of Fig. l;

nited States Patent ice Fig. 4 is a vertical sectional view of the clampaccording to the invention, corresponding to the view shown in Fig. 3and taken along the lines 44 of Fig. 3;

Fig. 5 is a vertical transverse sectional view, corresponding to theview of section 4 and taken along the line 55 of Fig. 5;

Fig. 6 is an elevational view of a spring button for use with the clampof the invention, and

Fig. 7 is an exploded perspective view of another embodiment.

Referring now to Fig. 1, the screen room 10 in which the clamp of thepresent invention is preferably used is of the type shown and describedin my copending application No. 338,136, now Patent No. 2,765,362.Individual screen sections 12 of standard size and construction areprovided with a shielding screen panel covering each face thereof inelectrically isolated relationship, as shown in Fig. 3 at 13, 14, 15 and16.

The screen should be made of highly conductive metal which possessesadequate tensile strength to withstand outline suspension, preferably 22mesh copperscreen wire or tinned ferrous wire to secure an effectivebarrier against emanation or invasion by radio waves within the bandssubject to examination. The attenuation in logarithmic units through ashield layer has been evaluated as proportional to the first power ofits thickness and to the square root of its conductivity, permeabilityand the Wave frequency.

The shielding BffiCiIlCY of the screens is related to their conductivityand uonpermeability as wellas to the preservation of continuouselectrical conductivity between contiguous parts. By utilizing multiplemutually spaced shielding enclosures formed of appropriate materials,the quality of wave attenuation may be improved and extended over a widerange of frequencies.

The effectiveness of attenuation has also been recognized as factoriallydependent upon the establishment of sufficient impedance in respectto'double shield screens and for this purpose each screen of a panel isrequired to be spaced and electrically insulated from the other. Theindividual screen panels form inner and outer screen layers each ofwhich completely encompasses the enclosure, and this achievement ofconductivity coupling between consecutive sections of the same screenand of isolation between the respective screen shields presents a uniquesituation, in which the clamp of the invention is especially useful.This is particularly the case where, as is preferred, the screen marginsoverlie the front edges of the sections as set forth in theaforementioned application No. 308A 36, now Patent No. 2,765,362.

The screen room sections 12 are formed by means .of a frame structurehaving spaced parallel side members adapted to be secured together alongtheir confronting edges with the adjacent screen panels in electricalcontact, the sides being recessed to secure the fastening means of theinvention as hereinafter set forth.

Referring now to Figures 2, 4 and 5, a clamp 18 is shown which comprisesan elongate rack 26 pivotally secured in a side member 220 f a frame 24by means of a removable bolt 26 and a detent assembly including a member238 journal'led on a metal plate Misecured in a side member 32 of aframe 34, a detent finger 36 journalled in the plate 30 having anabutment shoulder 38 integrally formed thereon and a leaf spring 4%secured by a bolt 41 to a transverse flange 43 on plate 30 for biasingthe detent finger into locking engagement upon rack 20.

The rack 29 is provided with a contoured or cutout portion 42 adjacentthe free end thereof, having a downwardly extending shoulder 44 adaptedto 'be engaged by a complementary contoured portion or shoulder '46 ofmember 28, and teeth 48rare also formed on the rack,

3 along the side opposite cutout portion 42, having a taperedconfiguration along a forward edge and a substantially vertical shoulder52 for engagement by detent 36 as will be hereinafter further described.

The side member or upright 22 is provided with an aperture 54intermediate the edges 56 and 58 covered by screens 13 and 14respectively and has the rack 20 pivotally secure-d thereto, the rack 20being disposed in parallel alignment with edges 56 and 58. Aperture 54is preferably of a height such as to permit the rack 20 to besubstantially retracted therein for transportation and storage. In usethe rack will be supported on a horizontally extending shelf or ledgeperpendicularly to upright 22 and in predetermined relation to member 28and detent 36 so that detent 36 as urged by spring 40, will ride overthe successive tapered edges 50 of the teeth of the rack when theuprights 22 and 32 are moved together with their frames 24 and 34 inparallel alignment, the rack being adapted to move inwardly at the sametime over member 28. A suitable spring (not shown) maybe provided tourge the member counter-clockwise so that shoulder 46 will not obstructthe rack.

The plate 30 is mounted within an aperture 62 in upright 32 by means ofa removable bolt 64, the upper and lower edges 66 and 68 of the platebeing preferably set in grooves 70 and 72 in parallel alignment withedges 74 and 76 covered by screens 15 and 16.

When the frames 24 and 34 are in coplanar relation apertures 54 and 62will be offset slightly so that the inward movement of the rack 20between member 28 and detent 36 will bring the rack '20 into theaperture 62 in relation with plate 30 as shown in Fig. 3, the rack andplate serving as guides to maintain the frames in proper alignment. Therack 20 may also ride upon bolt 64-, as

shown in Fig. 4, to further maintain the parts in a stable relationship.

After the uprights 22 and 32 have been guided into abutting relationshipas described, an Allen wrench 78 may be used to clamp them together byinserting an end of the wrench through aperture 77 in upright 32, into akeying recess 80 in the member 28 and rotating the member in a clockwisedirection in accordance with the embodiment shown in Fig. 4 so that theshoulder 46 on the member engages the shoulder 44 on contoured portion42 of the rack to draw the frames into firm engagement along thetransverse edges 84 and 86.

When the tightness of fit between the frames has been adjusted asdesired, the tension on the rack 20 is maintained by the detent 36,which locks against a shoulder 52 and is held against rotation in theclockwise direction by the bolt 64, which prevents rack 20 from movingdownwardly away from the detent in cooperation with the shelf 60. Afterthe frames are thus engaged, a spring button 88 may be used to coveraperture 77 and conceal the mechanism of the clamp, the legs 90 pressingagainst the walls of the aperture to hold the button securely therem.

In disassembling the screen room 10, the frames may be separated byextracting the bolt 26 so that the rack 20 is in disengaged relation tothe upright 22, or by extracting bolt 64 so that the detent 36 no longerholds the rack against outward movement, member 28 being also freelyrotatable so as not to oppose withdrawal of the rack.

As seen in Fig. 3, the marginal edges of screens 13, 14, 15 and 16 aredrawn inwardly over lands 9.2, 94, 96 and 98 respectively and setdownwardly into grooves 163, 102, 104 and 106. The screens are heldsecurely in the grooves by means of inserts, 108, 110, 112 and 114, butit is preferred that the portions of the screens overlying the lands bebowed slightly so as to assure contact between screen sections in thesame shielding layer. However, it will be appreciated that uprights 22and 32, for example, may be slightly out of alignment with one an other,where frames are notperfectly rectangular, and

also that the amount of bowing over the respective lands may varyslightly. Accordingly, it is very desirable to vary the tightness of fitbetween frames to compensate for such factors, in order that theattenuation quality of the screen room 10 may not be reduced. The clampof the invention makes it possible to adjust and maintain the tension onrack 20 as desired to accomplish these objectives, and in addition addsgreatly to the ease with which the frames can be assembled anddisassembled as described.

in Fig. 7, another embodiment of the clamp of the invention is shownwherein a cylinder 116 is provided in place of the member 28, having aradially offset lug 118 formed axially on one end thereof adjacent theperipheral edge 119, the peripheral edge 121 of the other end of thecylinder being toothed. A rack is pivotally secured to upright 22 of theframe 24, as described with respect to rack Ztl, and is provided with atransversely extending slot 122 whose width is preferably slightly morethan the diameter of lug 118 and whose length is substantially greaterthan the diameter of lug 118. The cylinder 116 is adapted to fitrelatively snugly in the aperture 77, and the slot 122 is positioned toreceive the lug 118 at its lower end when the frames 24 and 34 aredisposed in contiguous parallel relationship. A wrench 124, having aperipherally toothed cylindrical projection 126, is provided to engagewith the complementary peripheral edge 121 of cylinder 116, and it ispreferred that cylinder 116 have a length substantially less than bore77 so that the projection 126 of wrench 124 may be held securely in thebore while exerting torque force on the cylinder. When such force isexerted, the cylinder will rotate in position in bore 77, while lug 118will exert tension force on the rack 120 as it turns. The verticalcomponent of the angular rotation of lug 118 is accommodated by theaforementioned length of slot 122, so that the lug will move from oneend of the slot to the other as it is displaced horizontally to move therack as shown in dot-and-dash in Fig. 7.

Other methods of forming an operative connection between the wrench andthe cylinder may be visualized, but it will be appreciated that sincethe cylinder is journalled in a fixed position in bore 77, the frames 24and 34 will be drawn into adjustably snug abutting relationship byrotation of the cylinder as previously described, and this relationshipwill be maintained by the detent 36.

Although I have described my invention with reference to particularfeatures and advantages thereof, it will be obvious to those skilled inthe art that modifications in the details and principles of theinvention may be made without departing from the essential conceptthereof as set forth in the following claims:

I claim:

1. In a screen room for electric and radio wave attenuation comprising aplurality of screening sections each having a rectangular frame and ametallic screen secured to either side of said frame in electricallyspaced relation, a clamp for securing two of said sections together inabutting relation along corresponding side portions of their respectiveframes for continuous electrical contact between respective screenportions of said frames com prising an elongated rack secured to one ofsaid side portions having a contoured portion formed thereon, a memberjournalled to the other of said side portions and having a shoulderadapted to engage said contoured portion of said rack when said sideportions are moved into contiguous parallel relation and to draw saidside portions and said frames into tightly abutting relation when saidcam is turned to place said rack under tension force and detent meansadapted to engage with said rack to maintain said tension force thereon.

2. The construction according to claim 1 wherein said detent meanscomprises a detent finger and an abutment shoulder integrally formedtherewith, and spring means adapted to exert torque on said abutmentshoulder to hold said detent finger in locking engagement with said rackwhen saidrack is subjected to said clamping tension by said cam.

3. In a screen room for electric and radio wave attenuation comprising aplurality of screening sections each having a rectangular frame and ametallic screen secured to either side of said frame in electricallyspaced relation, a clamp for securing side members of said framestogether in abutting relationship comprising an elongated rackpivo-tally secured to the outer edge of one of said side membersintermediate the edges covered by said screens and parallel therewith,said rack having a contoured portion at the free end thereof, a platefixedly secured in an aperture formed in the outer edge of the other ofsaid side members intermediate the edges covered by said screen andparallel therewith, a member journalled to said plate and having ashoulder adapted to engage said contoured portion of said rack uponmovement of said outer edges of said side members into contiguousparallel relationship and to draw said outer edges and said frames intotightly abutting relationship when said member is turned to place saidrack under tension force, and detent means adapted to engage said rackto maintain said tension force thereon.

4. The construction according to claim 3 wherein said detent meanscomprise a detent finger and an abutment shoulder formed integrallytherewith, said finger and shoulder being journalled in said plate inpredetermined spaced relation to said member corresponding to the widthof said rack-bar, the contoured portion of said rack-bar being formed onone longitudinal edge thereof and the teeth of the rack portion of saidrack-bar being formed on the other longitudinal edge of said rack-bar,said detent being adapted to afford entry to said rack therebeneath andover said member when said detent and member are in the inoperativeposition, and a leaf spring having one end secured to said plate and theother end thereof hearing upon said abutment shoulder whereby tomaintain said rack under clamping tension in engagement with saiddetent.

5. The construction according to claim 4 wherein said first named sideportion is apertured to afford upward pivotal movement of said rack anda shelf is formed therein beneath said rack adapted to support said rackin register with the opening defined by said cam and detent.

6. The construction according to claim 3 wherein said rack is pivotallysecured to said first-named side portion by removable bolt means wherebyto afford suitable disengagement of said clamp.

7. The construction according to claim 6 wherein said plate is securedto said second named side portion by removable bolt means adapted tocooperate with said first named bolt means and affording suitabledisengagement of said clamp, said second named bolt means being adaptedto oppose pivotal movement of said rack away from said detent when saiddetent is in locking relationship with said clamp.

8. A fastening element for adjacent sections of a demountable enclosurecomprising .an elongated rack mountable on one of said sections saidrack including a depending shoulder, a detent assembly mountable on acorresponding edge of the other of said sections and operable tocooperate with said rack to secure the sections in fixed relation, saiddetent assembly including a spring biased detent finger and a rotatablemember having a shoulder adapted to engage said shoulder for lockingsaid sections in tightly abutting relation.

9. In a screen room for radio wave attenuation comprising a plurality ofscreening sections each having a rectangular frame and a metallic screensecured to either side of said frame in electrically spaced relation andturned inwardly at their marginal edges toward one another along theedges of said frames, a clamp for securing parallel edges of said framesin abutting relation with corresponding inwardly turned marginal edgesof said parallel edges in tightly abutting relationship comprising anelongate rack pivotally secured to one of said parallel edges and havinga contoured portion at the free end thereof, a detent member journalledin the other of said parallel edges, spring means associated therewithadapted to bring said detent member into locking engagement with saidrack when said edges are moved into abutting relation and manuallyoperable rotatable means on said other edge configured to engage saidcontoured portions of said rack to clamp said edge together.

10. In a screen door for electric and radio wave attenuation comprisinga plurality of screening sections each having a rectangular frame and ametallic screen secured to either side of said frame in electricallyspaced relation, a clamp for securing two of said sections together inabutting relation along corresponding side portions of their respectiveframes for continuous electrical contact between respective screenportions of said frames comprising an elongated rack pivotally securedto one of said side portions having a transversely extending slot formedin the free end thereof, a cylinder having a diameter substantiallygreater than the width of said slot, an axially extending lug on one endof said cylinder offset radially toward the periphery of said cylinderand adapted to be received in said slot, the other of said side portionsbeing cylindrically apertured to receive said cylinder relatively snuglytherein when said lug is in said slot, means for exerting torque on saidcylinder to place said rack under tension force when said lug is in saidslot whereby to draw said side portions and said frames into tightlyabutting parallel relation and detent means adapted to engage with saidrack to maintain said tension force thereon.

11. In a screen room for electric and radio wave attenuation comprisinga plurality of screeing sections each having a rectangular frame and ametallic screen secured to either side of said frame in electricallyspaced relation, a clamp for securing two of said sections together inabutting relation along corresponding side portions of their respectiveframes for continuous electrical contact between respective screenportions of said frames comprising an elongated rack pivotally securedto one of said side portions having a transversely extending slot formedin the free end thereof, a cylinder having a diameter substantiallygreater than the width of said slot, an axially extending lug on one endof said cylinder offset radially toward the periphery of said cylinderand adapted to be received in said slot, the other end of said cylinderbeing toothed peripherally, the other of said side portions beingcylindrically apertured to receive said cylinder relatively snuglytherein when said lug is in said slot, wrench means having aconfiguration complementary to the toothed configuration of saidcylinder for exerting torque on said cylinder to place said rack undertension force when said lug is in said slot whereby to draw said sideportions and said frames into tightly abutting parallel relation anddetent means adapted to engage with said rack to maintain said tensionforce thereon.

References Cited in the file of this patent UNITED STATES PATENTS

